This invention relates to a quick coupler for bucket excavators.
Hydraulically operated mechanical excavators have a dipper arm on the end of which are two mounting points by means of which an excavating bucket is pivotally attached to the end of the arm, and pivoted relative to the arm, respectively. Until relatively recently, if the operator wished to change the bucket, e.g. to a larger one, this had to be done manually. This involved the operator leaving the cab of the excavator, removing two pivot pins by means of which the bucket is connected to the dipper arm, getting back into the cab to lift the dipper arm clear of the bucket, aligning the dipper arm with the new bucket (and aligning the pivot apertures), de-mounting from the cab again, and locating the pivot pins in the aligned apertures, and securing them in place (e.g. with circlips, locking pins or bolts or the like) and then getting back into the cab to use the excavator. Sometimes, the operator would have considerable difficulty in removing or re-inserting the pivot pins, due to slight misalignment of the pivot apertures, and would have to use a heavy hammer for this purpose.
More recently, this time consuming exercise has been largely dispensed with, with the introduction of quick couplers which are located between the dipper arm and the bucket. Couplers of this type are disclosed, for example, in FR 2760029 and FR 2701047. FR 2760029 forms the basis of the preamble of claim 1 appended hereto. The couplers can either be of the hydraulic type or of the mechanical type and are effectively permanently fitted to the two pivot apertures of the dipper arm and the bucket pivoting link, respectively. These couplers incorporate a generally horizontally and rearwardly extending hook-like aperture or jaw adapted to engage with one of the pivot pins on the bucket (both of which are left fitted to the bucket), and a generally downwardly extending aperture or jaw adapted to locate over the other pivot pin on the bucket, with which downwardly extending aperture a moveable latching hook is associated.
In the manual version of the coupler, this latching hook is biased by a coil spring to its latching position, and is moved away from its latching position by a release handle or lever rod which is removably locatable in an aperture in the nose of the latching hook.
In the hydraulic version, a double acting hydraulic piston and cylinder device moves the latching hook between its respective positions, and check valves are located within the piston and cylinder device to prevent inadvertent movement of the piston in the event of hydraulic failure.
However, in both the manual and hydraulic versions, a safety pin has to be provided which must be located by the excavator operator in specially provided apertures in the coupler, to lock the latching hook in its latching position. This means that in both of these versions, the digger operator still has to leave his cab to secure in position the safety pin; this is inconvenient and time consuming.
It is an object of the present invention to provide a fully automatic coupler for an excavator bucket which can be operated by the excavator operator from his cab and be locked in its latching position without the operator having to leave the cab.
According to the present invention as defined in claim 1, we provide a coupler to enable an excavator operator to couple an excavator bucket (as herein defined) to a dipper arm of an excavator without leaving his cab, the coupler comprising two spaced side plates each having four fixed pin location points, the coupler being mountable in use between the bucket and the dipper arm and comprising a first aperture and a second aperture defining two of said points and connectable respectively, in use, to the dipper arm of the excavator and a bucket piston and cylinder device, by suitable pins, a first open-ended hook-like aperture defining a third of said points and for engagement with a first pivot pin provided on an excavator bucket, and a pivoting latching hook co-operating with a second open-ended aperture defining said fourth point and for latching engagement with a second pivot pin provided on the bucket once the first hook-like aperture has been engaged with the first pivot pin, in use, power operated means for moving the latching hook between latching and unlatched positions and operable by the operator from the cab, and blocking means adjustably supported on the body of the coupler and moveable from within the cab of the excavator from and into a blocking position in which it prevents the latching hook from being disengaged from the second pivot pin on the bucket.
In one preferred construction, the blocking means is moveable under its own weight by the force of gravity into a latch blocking position in which it prevents the latching hook from being disengaged from the second pivot pin on the bucket, and resiliently deformable means is provided on the blocking means which, in use, will engage an abutment when the coupler is inverted by rotation in one sense (with the result that the blocking means will tend under its own weight to move away from its blocking position) such engagement resulting in the resiliently deformable means biasing the blocking means into its latch blocking position.
In this construction, by inverting the coupler, the blocking means will move, under its own weight, to a fully crowded position in which it no longer blocks the latching hook.
Alternatively, a spring may be provided permanently to bias the blocking means into its blocking position, and means is provided to move the blocking means against the bias of the spring, so that it no longer blocks the latching hook. In one arrangement, said means is provided by a wire and pulley arrangement, the wire of which will tighten when the coupler is inverted, i.e. on full curl of the bucket, to move the blocking means out of its blocking position.
In an alternative construction, a small hydraulic cylinder could be provided to move the blocking means out of its blocking position, against the bias of the spring.
Preferably, the latching hook is operated by means of a double acting piston and cylinder device, one end of which is pivotally connected about a first pivot axis to the coupler, and the other end of which is pivotally connected to the latching hook.
In one construction, the blocking means comprises a bifurcated blocking bar, the two limbs of which are pivotally supported on the coupler, preferably on the said first pivot axis, and the opposite end of which bears against a face on the rear of the latching hook.
In another construction, the blocking means may comprise a single blocking bar pivotally supported at one end region on the coupler, preferably on the first pivot axis and adapted to bear at its opposite end against a face on the rear of the hook.
Preferably, the face is stepped so that the coupler can be used with different sized bucket pivot pin distances (known as pin spread).
Preferably, the resiliently deformable means comprises an upstanding resiliently deformable arm on the blocking bar which will bear against an abutment on the dipper arm when the coupler is inverted, e.g. when a bucket operating cylinder is retracted to pivot the bucket.
Preferably, a protection plate is fitted over the latching hook and blocking means, through which plate the resiliently deformable arm projects, the plate being provided to ensure that excavated material does not interfere with the operation of the blocking means. The plate may be welded or bolted in position. Hydraulic hoses for the double acting piston and cylinder device for operating the latching hook preferably pass through one or more apertures in the plate, but alternatively that the plate may carry two hydraulic hose couplings and on the inner side of the plate, the couplings are permanently connected by suitable hoses to the said piston and cylinder device. This allows further hoses leading from the main pressure system on the excavator to be connected and disconnected easily to the coupler.
The spring for biasing the blocking means into its blocking position (if provided) may be located between the protection plate and the blocking means.
Although the piston and cylinder device for the latching hook is provided with a check valve and the blocking means is provided, it is important that maximum provision is made to ensure that a bucket cannot accidentally become disconnected from the coupler, and preferably therefore, the latching hook is designed so that it will not rotate to a release position when under load, or when there is a hydraulic failure in the piston and cylinder device controlling the hook, and when the blocking means has failed.
In the known coupler, the hook has a profile which is such that, under the above conditions, and the hook is carrying the weight of the bucket, the forces acting on the pin are such that there is a moment about the pivot supporting the hook which will cause the hook to rotate to its unlatched position, thus releasing the bucket.
In the present invention, we preferably provide a hook which has a profile such that under the above conditions, and when the hook is carrying the weight of the bucket, and there would otherwise be a tendency for the hook to rotate to a release position, the pin will move along the internal concave surface of the hook, from a first position tending to unlatch the hook to one putting no unlatching force on the hook and thereafter to one tending to move the hook to a latching position.
For this purpose, the free end of the hook preferably has an upturned, extended nose, the inner face of which is concave and which is preferably connected to the normal concave internal surface of the hook by an internal planar portion.